Annual Sea-blite (Suaeda maritima)
Annual Sea-blite is not much to look at but is a common and much overlooked plant because it does not have nice flowers! In fact, it is just a dull green weed!
However, once the Spartina grass has established and started bring some solidity to the mud so Sea-blite can then establish. Although resistant to salt it tends to grow around high water where it rarely gets covered.
This is a common plant in its chosen environment.